In vivo effects of corticotropin-releasing factor in pregnant rats.
OBJECTIVE
Our purpose was to study the effects of corticotropin-releasing factor on (1) maternal blood pressure, (2) uterine vasculature, and (3) parturition in pregnant rats.


METHODS
Infusion minipumps containing vehicle, corticotropin-releasing factor, or alpha-helical corticotropin-releasing factor 9-41 (corticotropin-releasing factor receptor antagonist) were inserted subcutaneously in timed pregnant rats on day 16 of gestation. Systolic blood pressure was measured daily by the tail-cuff method. The time of onset of labor was determined and the newborn pups were weighed. Circulating levels of corticotropin-releasing factor were measured in untreated controls by radioimmunoassay. Relaxant responses to corticotropin-releasing factor were studied in isolated segments of uterine artery from late (day 18) and term (day 22) pregnant rats mounted in a wire myograph.


RESULTS
The blood pressure was decreased by corticotropin-releasing factor and increased by alpha-helical corticotropin-releasing factor 9-41 (p < 0.05). The time of onset of labor was not affected by either treatment. Pup weight was decreased by corticotropin-releasing factor (p < 0.05). Circulating levels of corticotropin-releasing factor (immunoreactive) were not changed in pregnancy. In vitro, corticotropin-releasing factor caused relaxation of the uterine artery in a concentration-dependent manner and the relaxation was decreased at term compared with late pregnancy (p < 0.05).


CONCLUSIONS
Endogenously produced corticotropin-releasing factor lowers blood pressure during pregnancy in rats. It is a relaxant of uterine vasculature and this effect is decreased at term. It does not play an essential role in the initiation of labor in rats.
Jain
V
V
Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston 77555-1062, USA.
Shi
S Q
SQ
Vedernikov
Y P
YP
Saade
G R
GR
Chwalisz
K
K
Garfield
R E
RE
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D001724:Birth Weight / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D015918:Infusion Pumps, Implantable; D007743:Labor, Obstetric / Q000187:drug effects* / Q000502:physiology; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D014599:Uterus / Q000098:blood supply* / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology
D010446:Peptide Fragments; D014665:Vasodilator Agents; D003346:Corticotropin-Releasing Hormone; C045089:corticotropin releasing hormone (9-41)